This is off the Mythic Warhammer site....
We have been hearing some rumblings out there from players who are having Authentication issues. We are currently investigating this, and we wanted to offer some advice in the meantime. If you’re having trouble logging into the servers, please be sure that you have done the following:
1. Create a Master Account using either a Beta Key or a Head Start Key in our Account Center at:
https://accounts.eamythic.com/
2. Enter your Warhammer Online keys to associate them with your Master Account
3. Use your Game Account login and password to log in to the game. Your Game Account login can be different from your Master Account login.
4. If you are unsure what your Game Account username is, consult the listing in the Account Management section of the Account Center. If you have forgotten your password, you may change it for each Game Account there, as well.
If you used a Head Start key to create your Master Account, you must either associate an Open Beta code with your account or wait until Head Start begins in order to play. If you are unsure which associations your Game Account has, click the Features tab for that account to check. Collector’s Edition Head Start begins on Sunday, Sept 14, and Standard Edition Head Start begins on Tuesday, September 16.
Please Note that we are no longer using the Beta Center for account validation. If you previously had a Beta Center account, you must create an account at the Account Center in order to play on our live (and open beta) servers.
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Not sure if that applies to you but I figured that I would let you